In the present study, the thermal performance of direct absorption solar evacuated tube collectors utilizing CuO nanofluid, CuO/Al2O3 binary nanofluid, and CuO nanofluid combined with microencapsulated phase change material (MPCM) is investigated. The impact of base fluid types (water and ethylene glycol (EG)), nanofluid volume fraction, and flow velocity, are analyzed by the numerical simulation of the collector. Also, two models (single-phase and mixture) are used for simulating the MPCM slurry. Due to the insignificant difference between the results of the single-phase and two-phase models, the single-phase model is recommended to reduce computational time. It is found that the most significant differences in outlet temperature occur using 0.06 % Al2O3+ 0.002 % CuO/water nanofluid and 0.06 % Al2O3+ 0.002 % CuO/EG nanofluid which are equal to 28.34 K, and 36.64 K, respectively. The collector efficiency using binary nanofluids is higher than using CuO nanofluids in both water- and EG-based nanofluids. Results indicate that combining MPCM and CuO nanofluid increases the collector efficiency by 4.53 % and lowers the heat loss by 5.84 %. The simultaneous application of MPCM and CuO nanofluid has the highest efficiency among all working fluids.